Companies found guilty of the practice could face millions of dollars in fines if prosecuted for the dumping, which is understood to be several cubic metres of waste in each case.

Demolition contractors must follow disposal guidelines, including paying any dumping fees at approved waste facilities, and there are strict requirements around the treatment of hazardous materials such as asbestos.

Environment Canterbury (ECan) confirmed buried waste had been found and removed at four properties, and another nine addresses were being investigated with ground-penetrating radar.